Antioxidant compositions

ABSTRACT

Antioxidant compositions containing (a) a sterically hindered phenol, (b) 4,4&#39;-bis(α,α-dimethylbenzyl) diphenyl amine and (c) a phenothiazine compound stabilize polyols against oxidative degradation and prevent urethane foams prepared therefrom from scorching.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.141,853 filed Apr. 21, 1980 U.S. Pat. No. 4,265,783.

BACKGROUND OF THE INVENTION

Antioxidants for polyether polyols and polyurethane foams preparedtherefrom are well known and include hindered phenols, phenothiazines,mixtures of hindered phenols with phenothiazines or phosphoric acid,mixtures of 2,6-ditertiarybutyl-4-methyl phenol and a dialkyldiphenylamine, mixtures of hindered phenol and4,4'-bis(α,α-dimethylbenzyl)diphenyl amine and mixtures of2,6-ditertiarybutyl-4-methyl phenol, p,p'-dioctyl diphenyl amine and aphenothiazine.

Because of fluctuation and/or availability of the component materials itis desirable to find ways to decrease the quantity of antioxidantnecessary to effectively stabilize the polyol and polyurethane againstoxidative degradation and the foams prepared therefrom from scorching.

It has now been unexpectedly discovered that polyether polyolsstabilized with a synergistic combination of certain hindered phenolsand 4,4'-bis(α,α-dimethylbenzyl) diphenyl amine with a phenothiazinecompound. The improvement is greater stability to the polyol againstoxidative degradation at the same level of antioxidant or reduced levelsof antioxidant for the same amount of stability.

SUMMARY OF THE INVENTION

One aspect of the present invention is directed to an improvement in apolyether polyol or mixture of polyether polyols stabilized againstoxidative degradations with a stabilizing quantity of a synergisticcomposition containing

(A) from about 15 to about 85, preferably from about 25 to about 75percent by weight of a sterically hindered phenolic antioxidant and

(B) from about 85 to about 15 and preferably from about 75 to about 25percent by weight of 4,4'-bis(α,α-dimethylbenzyl)diphenyl amine,

the improvement which comprises substituting for part of eithercomponent (A) or (B) or a part of each of components (A) and (B), fromabout 25 to about 1000, preferably from about 50 to about 500 parts permillion parts of polyether polyol of a phenothiazine compoundrepresented by the formula ##STR1## wherein each R is independentlyhydrogen or an alkyl group having from 1 to about 12 carbon atoms.

The present invention also pertains to polyurethane foams prepared fromthe aforementioned polyether polyol.

The present invention also pertains to antioxidant compositionscomprising

(A) from about 10 to about 85, preferably from about 20 to about 75percent by weight of a sterically hindered phenolic anioxidant;

(B) from about 10 to about 85, preferably from about 20 to about 75percent by weight 4,4'-bis(α,α-dimethylbenzyl) diphenyl amine; and

(C) from about 1 to about 34, preferably from about 2 to about 20percent by weight of a phenothiazine compound represented by the formula##STR2## wherein each R is independently hydrogen or an alkyl grouphaving from 1 to about 12 carbon atoms; and

wherein the weight ratio of component (A) to component (B) is from about0.17:1 to about 5.67:1, preferably from about 0.33:1 to about 3:1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Suitable sterically hindered phenolic antioxidant compounds which can beemployed herein include, for example,

2,4-dimethyl-6-octyl phenol,

2,6-ditertiarybutyl-4-methyl phenol,

2,6-ditertiarybutyl-4-ethyl phenol,

2,6-ditertiarybutyl-4-n-butyl phenol,

2,2'-methylene bis(4-methyl-6-tertiarybutyl phenol),

2,2'-methylene bis(4-ethyl-6-tertiarybutyl phenol),

2,4-dimethyl-6-tertiarybutyl phenol,

4-hydroxymethyl-2,6-ditertiarybutyl phenol,

n-octadecyl-beta (3,5-ditertiarybutyl-4-hydroxyphenyl) propionate,mixtures thereof and the like.

Particularly suitable phenothiazine compounds which can be employedherein include, for example, phenothiazine, 2-methylphenothiazine,3-octylphenothiazine, 2,8-dimethylphenothiazine,3,7-dimethylphenothiazine, 3,7-diethylphenothiazine,3,7-dibutylphenothiazine, 3,7-dioctylphenothiazine,2,8-dioctylphenothiazine, mixtures thereof and the like.

The polyether polyols which can be stabilized with the antioxidantcomposition of the present invention include those having from 2 toabout 8 OH groups. Such polyols are disclosed by and methods for theirpreparation are given in POLYURETHANES: CHEMISTRY AND TECHNOLOGY II.TECHNOLOGY by Saunders and Frisch, Interscience Publishers, 1964. Alsodescribed therein are polyurethane foams and methods for theirpreparation.

Particularly suitable polyether polyols include those prepared byreacting an initiator compound having 2 to about 8 hydroxyl groups withan alkylene oxide or mixtures of such oxides, said polyols havingmolecular weights of from about 250 to about 10,000, preferably fromabout 2,000 to about 8,000.

Suitable initiator compounds include, for example, ethylene glycol,propylene glycol, water, butane diol, hexane diol, glycerine,trimethylol propane, hexane triol, penaerythritol, sucrose, mixturesthereof and the like.

Suitable alkylene oxides include, for example, 1,2-propylene oxide,ethylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, styrene oxide,epichlorohydrin, epibromohydrin, mixtures thereof and the like.

The synergistic antioxidant compositions are employed in quantities ofat least 10 parts per million (ppm) based upon the polyether polyol,preferably from about 500 to about 100,000, most preferably from about1500 to about 5,000 ppm.

The following examples are illustrative of the present invention but arenot to be construed so as to limit the scope thereof in any manner.

The stability of the polyols containing the various antioxidant systemswas determined by placing the samples in a DuPont differential scanningcalorimeter, Model 990 Thermal Analyzer and Module, at the indicatedtemperature and the induction period (time to initiation of oxidativedecomposition) was recorded.

In the stability determination, the polyol samples weighing 10 mg±0.2 mgwere placed in an aluminum pan containing a disc of 100 mesh stainlesssteel wire screen in the bottom of the pan. The aluminum pan containingthe sample to be tested was placed in a differential scanningcalorimeter cell along with a reference pan containing only the wirescreen. The differential scanning calorimeter cell was purged withnitrogen for five minutes after it was closed. The cell was brought upto the isothermal temperature as quickly as possible withoutovershooting the desired temperature, usually 3 to 4 minutes. When thedesired temperature was reached, the nitrogen was turned off and oxygenwas introduced into the cell. When the oxygen flow rate reached 50cc/minute, the recorder was started. Time was recorded on the X axis ofthe recorder, the temperature profile of the run was recorded on the Yaxis, and the energy emitted or absorbed by the sample was recorded onthe Y' axis. The induction period (time between introduction of oxygeninto the cell and the time of initiation of oxidative decomposition) wasdetermined by locating the point of interception of the baseline (Xaxis) and the slope of the exotherm deflection (Y' axis). The longer theinduction period of the sample, the more stable was the sample.

EXAMPLE 1

Various levels of 2,6-ditertiarybutyl-4-methyl phenol,4,4'-bis(α,α-dimethylbenzyl)diphenyl amine and phenothiazine wereemployed to stabilize a polyether polyol against oxidative degradation.The polyol employed was the reaction product of a mixture 92 wt. percentpropylene oxide and 8 wt. percent ethylene oxide with aglycerine-propylene oxide reaction product having a molecular weight ofabout 450, the resultant polyol having a molecular weight of about 3000hereinafter designated as polyol A.

Resistance to foam scorch was determined by preparing low densityflexible foam with the polyols containing the various antioxidantsystems and then subjecting these foams to a scorch test. The foams wereprepared by a one-shot process using the following formulation:

    ______________________________________                                        (1)   3000 molecular weight polyether                                               polyol A             200 grams                                          (2)   Water                10.4 grams                                         (3)   L-540 Silicone surfactant                                                                          2.4 grams                                          (4)   Niax A-6 Amine catalyst                                                                            0.250 grams                                        (5)   T-9 Stannous octoate 0.300, 0.350,                                                                 or 0.400 grams                                     (6)   80/20 mixture of                                                              2,4-2,6-toluene diisocyanate                                                  (120 Index)          141.9 grams                                        ______________________________________                                    

The first five components of the formulation were mixed at 2000 rpm in aone quart Dixie cup for 25 seconds. The toluene diisocyanate was addedto the cup and the components were mixed for an additional 5 seconds at2000 rpm. Immediately after the second mix the formulation was pouredinto a 10 inch×10 inch×4 inch pastry box. The foam was allowed to riseand at 300 seconds from the start of the second mix the foam bun wasplaced into a preheated microwave oven for 4 minutes. The microwave ovenhad been calibrated so that 400 grams of water would increase 44° C. intemperature when heated for 4 minutes. At the end of the microwave curethe foam bun was placed in a conventional air circulating oven,controlled at 100° C., for 30 minutes. The foam buns were then allowedto cure at room temperature for 18 hours.

After a final cure of the foam buns, a one inch thick slice was cutparallel to the rise from the center of each bun. Each foam slice wasthen placed on a light box and the color of the foam was observed. Thebreathability (airflow) in the direction of foam rise was measured on a2 inch×2 inch×1 inch foam sample taken from the center of the remainingportion of the foam bun.

One foam bun was prepared at each of the three stannous octoate levelswith each polyol evaluated in the scorch test. The degree of foam scorchis related to the breathability (a relative measure of the open cellcontent) of the foam which is related to the amount of stannous octoatein the formulation. In this scorch test, the degree of scorch increasedwith the increased breathability. When the same base polyol is used inthe foam formulation equivalent air flow values are obtained at aconstant stannous octoate level. Therefore the resistance to scorch wascompared at equivalent air flow values. The degree of scorch is alsorelated to the absolute humidity and only the foams made under the samehumidity conditions are comparable.

The results of the stability and scorch resistance determination forthis example are presented in Table I. In this table "BHT" stands for2,6-ditertiarybutyl-4-methyl phenol, "DMBDPA" stands for4,4'-bis(α,α-dimethylbenzyl)diphenyl amine, "PTZ" stands forphenothiazine, and "I.P." stands for induction period. The foamappearance was rated as follows:

0 White, no discoloration

1 Very slight yellow discoloration

2 Light yellow discoloration

3 Yellow discoloration

4 Yellow to light brown discoloration

5 Yellow brown discoloration

6 Dark yellow brown discoloration

7 Opaque dark brown appearance

8 Charred dark brown with foam deterioration

9 Severe scorch, the foam actually started to smolder

                                      TABLE I                                     __________________________________________________________________________                                       Average                                         Antioxidant Level,                                                                        I.P. at                                                                            Foam Appearance Rating                                                                     Appear-                                    Sample                                                                             ppm         170° C.,                                                                    @ Various T-9 Wts. (gms).sup.1                                                             ance                                       Number                                                                             BHT                                                                              DMBDPA                                                                              PTZ                                                                              min. 0.300                                                                             0.350                                                                             0.400                                                                              Rating                                     __________________________________________________________________________    1.sup.2                                                                            3000                                                                             1500  -- 22.9 5   4   3    4                                          2.sup.2                                                                            2000                                                                             1000  -- 15.8 9   7   5    7                                          3.sup.3                                                                            1900                                                                             1000  100                                                                              24.9 5   4   3    4                                          4.sup.3                                                                            2000                                                                              900  100                                                                              27.5 5   4   3    4                                          5.sup.2                                                                            -- --    100                                                                              11.5 9   9   8    8.7                                        __________________________________________________________________________     .sup.1 These foam samples were prepared when the absolute humidity ranged     from 99 to 102 grains of water per pound of dry air.                          .sup.2 Comparative Experiment.                                                .sup.3 Example of the present invention.                                 

EXAMPLE 2

The polyether polyol described in Example 1 was stabilized with 3300 ppmtotal antioxidant while the amounts of 2,6-ditertiarybutyl-4-methylphenol, 4,4'-bis(α,α-dimethylbenzyl)diphenyl amine and phenothiazine ineach composition were varied. These polyol samples were then evaluatedas described in Example 1 and the data is presented in Table II.

                                      TABLE II                                    __________________________________________________________________________                                       Average                                         Antioxidant Level,                                                                        I.P. at                                                                            Foam Appearance Rating                                                                     Appear-                                    Sample                                                                             ppm         170° C.,                                                                    @ Various T-9 Wts. (gms).sup.1                                                             ance                                       Number                                                                             BHT                                                                              DMBDPA                                                                              PTZ                                                                              min. 0.300                                                                             0.350                                                                             0.400                                                                              Rating                                     __________________________________________________________________________    6.sup.2                                                                            2200                                                                             1100  -- 14.7 9   7   5    7                                          7.sup.3                                                                            2150                                                                             1100   50                                                                              23.5 9   5   4    6                                          8.sup.3                                                                            2200                                                                             1050   50                                                                              20.6 7   5   3    5                                          9.sup.3                                                                            2100                                                                             1100  100                                                                              28.1 5   3   3    3.7                                        10.sup.3                                                                           2200                                                                             1000  100                                                                              30.1 5   3   3    3.7                                        __________________________________________________________________________     .sup.1 These foam samples were prepared when the absolute humidity ranged     from 98 to 103 grains of water per pound of dry air.                          .sup.2 Comparative Experiment.                                                .sup.3 Example of the present invention.                                 

EXAMPLE 3

The polyether polyol described in Example 1 was stabilized with 3000 ppmtotal antioxidant while the amounts of 2,6-ditertiarybutyl-4-methylphenol, 4,4'-bis(α,α-dimethylbenzyl)diphenyl amine and phenothiazine ineach composition were varied. These polyol samples were then evaluatedas described in Example 1 and the data is presented in Table III.

                                      TABLE III                                   __________________________________________________________________________                                       Average                                         Antioxidant Level,                                                                        I.P. at                                                                            Foam Appearance Rating                                                                     Appear-                                    Sample                                                                             ppm         170° C.,                                                                    @ Various T-9 Wts. (gms).sup.1                                                             ance                                       Number                                                                             BHT                                                                              DMBDPA                                                                              PTZ                                                                              min. 0.300                                                                             0.350                                                                             0.400                                                                              Rating                                     __________________________________________________________________________    11.sup.2                                                                           1500                                                                             1500  -- 14.5 9   8   7    8                                          12.sup.3                                                                           1450                                                                             1500   50                                                                              20.2 5   7   5    5.7                                        13.sup.3                                                                           1500                                                                             1450   50                                                                              23.1 5   3   6    4.7                                        14.sup.3                                                                           1400                                                                             1500  100                                                                              26.8 5   6   3    4.7                                        15.sup.3                                                                           1500                                                                             1400  100                                                                              28.4 5   3   3    3.7                                        __________________________________________________________________________     .sup.1 These foam samples were prepared when the absolute humidity ranged     from 66 to 78 grains of water per pound of dry air.                           .sup.2 Comparative Experiment.                                                .sup.3 Example of the present invention.                                 

EXAMPLE 4

The polyether polyol described in Example 1 was stabilized with variousamounts of 2,6-ditertiarybutyl-4-n-butyl phenol,4,4'-bis(α,α-dimethylbenzyl) diphenyl amine, and phenothiazine todemonstrate the utility of this invention while using a different typeof hindered phenolic antioxidant. The total stabilizer level was heldconstant at 3600 ppm. These polyol samples were evaluated as describedin Example 1. The data for this example is presented in Table IV where"DTBNBP" stands for 2,6-ditertiarybutyl-4-n-butyl phenol and all otherabbreviations are the same as defined in Example 1.

                                      TABLE IV                                    __________________________________________________________________________                                           Average                                     Antioxidant Level,                                                                           I.P. at                                                                            Foam Appearance Rating                                                                      Appear-                                Sample                                                                             ppm            170° C.,                                                                    @ Various T-9 Wts. (gms).sup.1                                                              ance                                   Number                                                                             DTBNBP                                                                              DMBDPA                                                                              PTZ                                                                              min. 0.300                                                                              0.350                                                                             0.400                                                                              Rating                                 __________________________________________________________________________    16.sup.2                                                                           2400  1200  -- 17.0 9    8   5    7.3                                    17.sup.3                                                                           2325  1200   75                                                                              29.5 5    4   4    4.3                                    18.sup.3                                                                           2400  1125   75                                                                              27.0 5    4   3    4                                      19.sup.3                                                                           2250  1200  150                                                                              32.6 5    4   3    4                                      20.sup.3                                                                           2400  1050  150                                                                              37.2 4    3   3    3.3                                    __________________________________________________________________________     .sup.1 These foam samples were prepared when the absolute humidity ranged     from 63 to 69 grains of water per pound of dry air.                           .sup.2 Comparative Experiment.                                                .sup.3 Example of the present invention.                                 

EXAMPLE 5

Various levels of several hindered phenolic antioxidants,4,4'-bis(α,α-dimethylbenzyl) diphenyl amine and phenothiazine wereemployed to stabilize either Polyol A or Polyol B. Polyol A wasdescribed in Example 1. Polyol B was the reaction product of propyleneoxide with a glycerine-propylene oxide reaction product having amolecular weight of about 450, the resultant polyol having a molecularweight of about 3000. The results of the polyol stability determinationare presented in Table V. The hindered phenolic antioxidants wereabbreviated as follows:

BHT: 2,6-ditertiarybutyl-4-methyl phenol

DMOP: 2,4-dimethyl-6-octyl phenol

DMTBP: 2,4-dimethyl-6-tertiarybutyl phenol

MBMTBP: 2,2'-methylene bis(4-methyl-6-tertiarybutyl phenol)

MBETBP: 2,2'-methylene bis(4-ethyl-6-tertiarybutyl phenol)

HDTBP: 4-hydroxymethyl-2,6-ditertiarybutyl phenol

ODTBHPP: n-octadecyl-beta (3,5-ditertiarybutyl-4-hydroxyphenyl)propionate

All other appreviations are the same as defined in Example 1.

                                      TABLE V                                     __________________________________________________________________________    SAMPLE      PHENOLIC ANTIOXIDANT LEVEL, ppm                                                                        I.P. TEMP.                                                                           I.P.                              NUMBER                                                                              POLYOL                                                                              ANTIOXIDANT                                                                            PHENOLIC                                                                             DMBDPA                                                                              PTZ                                                                              °C.                                                                           MIN.                              __________________________________________________________________________    21.sup.1                                                                            B     BHT       250    250  -- 140    19.7                              22.sup.2                                                                            B     BHT       225    250   25                                                                              140    47.7                              23.sup.2                                                                            B     BHT       250    225   25                                                                              140    32.5                              24.sup.1                                                                            B     BHT      5000   5000  -- 180    19.6                              25.sup.2                                                                            B     BHT      4500   5000  500                                                                              180    38.8                              26.sup.2                                                                            B     BHT      5000   4500  500                                                                              180    35.7                              27.sup.1                                                                            A     DMOP     2400   1200  -- 170    12.5                              28.sup.2                                                                            A     DMOP     2325   1200   75                                                                              170    16.9                              29.sup.2                                                                            A     DMOP     2400   1125   75                                                                              170    14.8                              30.sup.2                                                                            A     DMOP     2250   1200  150                                                                              170    20.7                              31.sup.2                                                                            A     DMOP     2400   1050  150                                                                              170    18.0                              32.sup.1                                                                            B     DMTBP    1500   1500  -- 170    10.9                              33.sup.2                                                                            B     DMTBP    1400   1500  100                                                                              170    17.3                              34.sup.2                                                                            B     DMTBP    1500   1400  100                                                                              170    19.4                              35.sup.1                                                                            B     MBMTBP   1000   1000  -- 170    12.9                              36.sup.2                                                                            B     MBMTBP    900   1000  100                                                                              170    20.1                              37.sup.2                                                                            B     MBMTBP   1000    900  100                                                                              170    20.8                              38.sup.1                                                                            B     MBETBP   1500   1500  -- 170    14.3                              39.sup.2                                                                            B     MBETBP   1400   1500  100                                                                              170    22.5                              40.sup.2                                                                            B     MBETBP   1500   1400  100                                                                              170    25.2                              41.sup.1                                                                            B     HDTBP    1500   1500  -- 170    27.2                              42.sup.2                                                                            B     HDTBP    1400   1500  100                                                                              170    38.4                              43.sup.2                                                                            B     HDTBP    1500   1400  100                                                                              170    41.3                              44.sup.1                                                                            B     ODTBHPP  1500   1500  -- 170    14.6                              45.sup.2                                                                            B     ODTBHPP  1400   1500  100                                                                              170    36.5                              46.sup.2                                                                            B     ODTBHPP  1500   1400  100                                                                              170    36.5                              __________________________________________________________________________     .sup.1 Comparative Experiment                                                 .sup.2 Example of the present invention                                  

I claim:
 1. An antioxidant composition comprising(A) from about 10 toabout 85 percent by weight of a hindered phenolic antioxidant; (B) fromabout 10 to about 85 percent by weight of 4,4'-bis(α,α-dimethylbenzyl)diphenyl amine; and (C) from about 1 to about 34 percent by weight of aphenothiazine compound represented by the formula ##STR3## wherein eachR is independently hydrogen or an alkyl group having from 1 to about 12carbon atoms; andwherein the weight ratio of component (A) to component(B) is from about 0.17:1 to about 5.67:1.
 2. A composition of claim 1wherein(a) component (A) is present in quantities of from about 20 toabout 75 percent by weight; (b) component (B) is present in quantitiesof from about 20 to about 75 percent by weight; (c) component (C) ispresent in quantities of from about 2 to about 20 percent by weight; and(d) the weight ratio of component (A) to component (B) is from about0.33:1 to about 3:1.
 3. A composition of claims 1 or 2 wherein(a) saidsterically hindered phenol is selected from the group consistingof2,4-dimethyl-6-octyl phenol, 2,6-ditertiarybutyl-4-methyl phenol,2,6-ditertiarybutyl-4-ethyl phenol, 2,6-ditertiarybutyl-4-n-butylphenol, 2,2'-methylene bis(4-methyl-6-tertiarybutyl phenol),2,2'-methylene bis(4-ethyl-6-tertiarybutyl phenol),2,4-dimethyl-6-tertiarybutyl phenol, 4-hydroxymethyl-2,6-ditertiarybutylphenol, n-octadecyl-beta(3,5-ditertiarybutyl-4-hydroxyphenyl)propionate, mixtures thereof and the like; and (b) said phenothiazinecompound is selected from the group consisting of phenothiazine,2-methylphenothiazine, 3-octylphenothiazine, 2,8-dimethylphenothiazine,3,7-dimethylphenothiazine, 3,7-diethylphenothiazine,3,7-dibutylphenothiazine, 3,7-dioctylphenothiazine,2,8-dioctylphenothiazine, and mixtures thereof.
 4. A composition ofclaim 3 wherein said sterically hindered phenol is selected from thegroup consisting of2,4-dimethyl-6-octyl phenol,2,6-ditertiarybutyl-4-methyl phenol, 2,6-ditertiarybutyl-4-ethyl phenol,2,6-ditertiarybutyl-4-n-butyl phenol, 2,2'-methylenebis(4-methyl-6-tertiarybutyl phenol), 2,2'-methylenebis(4-ethyl-6-tertiarybutyl-phenol), and mixtures thereof.
 5. Acomposition of claim 4 wherein the sterically hindered phenol is2,6-ditertiarybutyl-4-methyl phenol and the phenothiazine compound isphenothiazine.